package multireader

import (
	"bytes"
	"io"
	"math/rand"
	"sync"
	"testing"
)

func TestMultiRead(t *testing.T) {
	t.Run("positive", func(t *testing.T) {
		_ = NewMultiReader(64)
	})
	t.Run("zero", func(t *testing.T) {
		_ = NewMultiReader(0)
	})
	t.Run("negative", func(t *testing.T) {
		_ = NewMultiReader(-64)
	})
}

func TestReadWrite(t *testing.T) {
	var (
		src  []byte
		dst1 []byte
		dst2 []byte
		dst3 []byte
		wg   *sync.WaitGroup
	)

	src = make([]byte, 20480)
	dst1 = make([]byte, 20480)
	dst2 = make([]byte, 20480)
	dst3 = make([]byte, 20480)

	n, err := rand.Read(src)
	if n < len(src) || err != nil {
		t.Fatalf("cannot initiate test data: %d; %v", n, err)
	}

	m := NewMultiReader(512)
	r1 := m.NewReader()
	r2 := m.NewReader()
	r3 := m.NewReader()
	wg = &sync.WaitGroup{}

	writeFunc := func(t *testing.T, m *MultiReader, data []byte, wg *sync.WaitGroup) {
		var (
			n        int
			dl       int
			r        int
			loopFlag bool
		)
		defer wg.Done()

		for n < len(data) {
			dl = rand.Intn(512)
			if n+512+dl > len(data) {
				r, _ = m.Write(data[n:])
			} else {
				r, _ = m.Write(data[n : n+512+dl])
			}
			n += r
			if rand.Intn(5) == 0 {
				loopFlag = false
				for !loopFlag {
					if rand.Intn(100) == 0 {
						loopFlag = true
					}
				}
			}
		}
		_ = m.Close()
	}
	wg.Add(1)
	go writeFunc(t, m, src, wg)

	readFunc := func(t *testing.T, r *Reader, data []byte, wg *sync.WaitGroup, split bool) {
		var (
			offset int
			n      int
			err    error
		)
		defer wg.Done()

		offset = 0
		for {
			if offset+1024 < len(data) {
				if split {
					_, err = r.WaitAvailable()
					if err != nil {
						t.Logf("reader got error on WaitAvailable: %v", err)
						break
					}
					n, err = r.ReadAhead(data[offset : offset+1024])
					if err != nil {
						t.Logf("reader got error on ReadAhead: %v", err)
						break
					}

					n -= 5
					_, err = r.Seek(int64(n), io.SeekCurrent)
					if err != nil {
						t.Logf("reader got error on Seek: %v", err)
						break
					}
				} else {
					n, err = r.Read(data[offset : offset+1024])
					if err != nil {
						t.Logf("reader got error: %v", err)
						break
					}
				}
			} else {
				n, err = r.Read(data[offset:])
				if err != nil {
					t.Logf("reader got error: %v", err)
					break
				}

			}
			offset += n
		}
	}

	wg.Add(1)
	go readFunc(t, r1, dst1, wg, false)
	wg.Add(1)
	go readFunc(t, r2, dst2, wg, false)
	wg.Add(1)
	go readFunc(t, r3, dst3, wg, true)

	wg.Wait()
	if !bytes.Equal(src, dst1) {
		t.Error("src and dst1 mismatch")
	}
	if !bytes.Equal(src, dst2) {
		t.Error("src and dst2 mismatch")
	}
	if !bytes.Equal(src, dst3) {
		t.Error("src and dst3 mismatch")
	}
}

func TestReaderClose(t *testing.T) {
	var (
		m                    *MultiReader
		r1                   *Reader
		r2                   *Reader
		r3                   *Reader
		src, dst, dst1, dst3 []byte
		err                  error
		found                bool
		ctr                  int
	)

	src = make([]byte, 16)
	dst = make([]byte, 32)
	dst1 = dst[:16]
	dst3 = dst[16:]
	m = NewMultiReader(0)
	r1 = m.NewReader()
	r2 = m.NewReader()
	r3 = m.NewReader()

	_, _ = rand.Read(src)
	_, err = m.Write(src)
	if err != nil {
		t.Fatalf("error setting up data: %v", err)
	}

	found = false
	for ctr = range m.pos {
		if m.pos[ctr].id == r2.id {
			found = true
			break
		}
	}
	if !found {
		t.Error("unexpected behavior, r2 should exist in reader position list")
	}

	_ = r2.Close()
	_, err = r2.Read(dst)
	if err == nil && err != ErrReaderClosed {
		t.Error("unexpected behavior, r2 should be closed")
	}

	found = false
	for ctr = range m.pos {
		if m.pos[ctr].id == r2.id {
			found = true
			break
		}
	}
	if found {
		t.Error("unexpected behavior, r2 should be removed from reader position list")
	}

	_, err = r1.Read(dst1)
	if err != nil {
		t.Errorf("failing to read from r1")
	}
	if !bytes.Equal(dst1, src) {
		t.Error("invalid result reading from r1")
	}

	_ = m.Close()
	_, err = r3.Read(dst3)
	if err != nil {
		t.Errorf("unexpected behavior, cannot read form r3: %v", err)
	}
	if !bytes.Equal(src, dst3) {
		t.Error("invalid result reading from r3")
	}

	_, err = r3.WaitAvailable()
	if err == nil {
		t.Error("unexpected behavior; WaitAvailable when readpos == lastWritePos should fail")
	}

	_, err = r3.ReadAhead(dst3)
	if err == nil {
		t.Error("unexpected behavior; ReadAhead when readpos == lastWritePos should fail")
	}

}